Ecological carrying capacity of public green spaces as a sustainability index of urban population; a case study of Mashhad city in Iran

Urban planners usually define carrying capacity as the ability of a natural zone or a built area to absorb population or development without any risk for both zone and population. This research aims to expand a framework for investigation of urban carrying capacity, which can determine a sustainability index of urban population based on public green spaces. For this purpose, a conventional three-level procedure of ecological carrying capacity for public green spaces was considered in Mashhad city, Iran. In this regard, the physical, real and effective carrying capacities were estimated for total public green spaces in Mashhad as about 68, 22 and 44% from total population, respectively. Furthermore, among Mashhad municipality districts, two districts represented the highest values of carrying capacity and high classes of ecological carrying capacity index over than 1 in Mashhad city due to accessibility to the natural patches and man-made gardens.